Warning: Very speculative.
This is how I could imagine SWIFT playing the game: Even though it is a cooperative of banks it seems they are working in competition to Ripple. Gottfried creating SWIFT gpi instead of working with Ripple is one example.
The issue for SWIFT is that Ripple offers the full package, could entirely replace SWIFT. It seems SWIFT gpi has become a lot more competitive to xCurrent lately. A fire was lit under their ass by Ripple.
What Ripple offers that no one else can offer is on-demand liquidity. This is the future, nostro vostro will die out, it's just a matter of time.
This is why I find it likely SWIFT would want to use Corda Settler with XRP to gain this massive advantage.
By doing this, they remove the biggest advantage to Ripplenet, on-demand liquidity. This would make banks want to stay with SWIFT most likely instead of switching to Ripplenet.
Behaviour from Ripple makes me believe this might be the case. You see that Ripple has been communicating a focus on remittance, not so much banks. Perhaps because if banks could get on-demand liquidity through SWIFT through Corda Settler they wouldn't find
enough incentive to switch to Ripplenet.
Another point I would like to raise is Marcus Treacher being pretty aggressive towards SWIFT, a former SWIFT employee going to Ripple. He mentions replacing SWIFT entirely, that they are not needed.
If Ripple were collaborating with SWIFT, I'm not so sure he would be so aggressive, right?
A possible scenario would be if SWIFT were collaborating with Ripple early on and learnt from Ripple... then switching and going with R3 and Corda Settler instead.
Marcus Treacher's harsh rhetoric would then make sense. Just speculation but it seems some things are going on behind the scenes. Lately news of SWIFT trialing Ripple for settlement, or could it be Corda Settler? XRP they talk about?
By doing this, SWIFT could continue to rule and Ripple could gain the much smaller remittance market and continue to expand XRP usage to other businesses through xPring.